It is known that skin damage can stimulate the growth of new collagen. Uncontrolled skin damage may cause scarring, which is excessive collagen growth. However, controlled damage of the skin which is intentionally introduced can stimulate controlled re-growth of collagen in such a way as to improve the appearance of the skin. A well known method of controlled skin damage is ablating the epidermis using laser radiation with wavelengths having strong water absorption. Typical lasers used for epidermal ablation are CO2 and Er:YAG lasers. U.S. Pat. No. 6,309,387 to Eggers et al. discloses ablation of the epidermis using RF current. This treatment significantly reduces wrinkles and improves skin appearance. The main disadvantages of skin resurfacing are the long healing period that can last for more than a month, and a high risk of dischromia. These disadvantages have reduced the popularity of ablative skin resurfacing.
Non-ablative skin resurfacing is based on heating the dermis up to a sub-necrotic temperature with simultaneous cooling of the skin surface. U.S. Pat. No. 5,810,801 to Anderson et al. describes the use of infrared laser radiation penetrating into the skin dermis with dynamic cooling of the skin surface using a cryogen spray. U.S. Pat. No. 5,755,753 to Knowlton describes a method of skin tightening using uni-polar or bi-polar RF electrodes to create skin heating in combination with cooling to generate a negative skin temperature gradient in which the dermis is hotter than the epidermis. The main barrier for introducing RF current is the stratum cornea, which should be hydrated by an electrolytic type of liquid prior the treatment. Non-ablative treatment is much safer and has no down time but the results of the treatment are less satisfactory.
A method described in US patent publication 20030216719 tries to retain the efficiency of ablative treatment coupled with a shorter healing time and with a lower risk of adverse effects. The device described in this patent publication coagulates fragments of the skin having a size in the range of tens of microns while keeping the distance between the fragments larger than the damaged zone. This treatment provides skin healing within a few days, but the results are very superficial and less satisfactory than with a CO2 laser, even after multiple sessions.